Relationship between soil movement and changes of forest floor environments after clearing in the northernmost region of Okinawa island
2019
Ohnuki, Y. (Forestry and Forest Products Research Institute (Japan). Tohoku Research Center) | Furugen, H. | Ikuzawa, H. | Matsuura, T. | Yamashita, N. | Arakaki, T.
To quantitatively clarify the distinct impact of forest clearing, soil movement was investigated using sediment trap boxes in and out of the cutover area. After collecting and studying the data related to the micro-topography, slope inclination and floor cover percentage, the difference of soil movement and seasonal changes were evaluated at 30 points in 6 plots. The amount of soil movement changed after the seasonal precipitation events, where the winter season was less than summer typhoon season, and both were less than the rainy season prior to summer owing to the brunt of only two typhoons. The data showed the largest value during the typhoon season, especially in a plot that was severely disturbed by heavy machinery. Steep forest plots also displayed rather large values in soil amount. By contrast, regardless of the amount of precipitation, the plots primarily covered with understory vegetation demonstrated low values similar to the plots located on gentle slopes in forests. Considering the relationship between the amount of soil movement, slope inclination, floor cover percentage and soil thickness; the understory vegetation was shown to have a significant influence on soil movement. However, when the floor cover percentage was approximately 50% or below, the amount of soil movement was more dependent on slope inclination and soil thickness.
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